As a gas meter of the related art which specifies a used appliance in a fluid piping system having a gas meter, a gas meter described in Patent Literature 1 is known. The configuration will be described with reference to FIG. 19.
As shown in FIG. 19, a gas meter 1 is disposed in a flow channel 6 connected to a household gas supply line. The gas meter 1 has flow rate measurement unit 3 for measuring a gas flow rate at a regular time interval, calculation unit 4 for calculating a differential in the flow rates output from the flow rate measurement unit 3, and comparison/determination unit 7 for comparing in magnitude the differential calculated by the calculation unit 4 with a change determination value registered in storage unit 5 and determining a change in the state of usage of the gas appliance. The calculation unit 4, the comparison/determination unit 7, and a gas shutoff valve 2 are controlled by a control circuit 116.
In the gas meter 1, the change in the differential of the instantaneous flow rate output from the flow rate measurement unit 3 is sequentially calculated, and the change in the state of usage of the gas appliance is determined on the basis of the amount of change. Registered data and the measured change (differential) in the gas flow rate are compared, thereby enabling identification of used gas appliances 13, 14, and 15.
As a method of identifying the used appliance of the fluid in the related art, a method described in Patent Literature 2 is known. The configuration will be described with reference to FIG. 20.
As shown in FIG. 20, a calculation unit 108 calculates the differentials of the gas flow rate measured by flow rate measurement unit 104 at regular intervals, and a differential conversion unit 112 classifies the differentials at regular time intervals into predetermined classifications using a flow rate classification table 110a stored in flow rate classification table holding unit 110, and converts the differentials to predetermined codes representing the classifications. An appliance identification unit 116 compares a code sequence generated by code sequence generation unit 114 using the codes converted by the differential conversion unit 112 with appliance-specific characteristic code sequences specific to the appliances stored in an appliance-specific code sequence information holding unit 118, and identifies the appliances.
In the above configuration, a code value obtained by encoding (converting) the differential of the flow rate is used, and at the time of appliance identification, calculation is simplified, thereby reducing the amount of memory or the like necessary for calculation and achieving improvement in calculation speed and appliance identification precision.